-4.2% is the change from 857 to 821
Calculation steps:
[( 821 - 857 ) ÷ 857] x 100 = -4.2%
Formula
Percentage change = [(821 - 857) / 857] x 100
Subtract the new number by the original number
821 - 857 = -36
-36 ÷ 857 = -0.042007001166861145
-0.042007001166861145 x 100 = -4.2%